Thanks for above. I tried re-installing open office (repair, which mentioned fixing registry problems), but the program does still not appear on the "open with" list. So many of my documents will open with media player. I would like to make Open Office my default program, but not sure how to do this. Windows 10. Can you help please?

You may need someone with more computer experience to look at the problem first-hand. I've never known repairing not to work. You may have some kind of protective programs installed that's preventing the AOO installation from modifying the registry settings. I no longer have Windows 10 to check, but AFAIK, media players shouldn't appear on the Open List with for .odt files. I do know that AOO Writer always appeared on my Open With lists for .odt files

Also, if you're using Windows 10, please change your signature. Windows 10 and Windows 8 can have very different problems and solutions.